Fire visibilityChange event on out-of-process iframes.

third_party/WebKit/public/web/WebFrameClient.h

Index: third_party/WebKit/public/web/WebFrameClient.h
diff --git a/third_party/WebKit/public/web/WebFrameClient.h b/third_party/WebKit/public/web/WebFrameClient.h
index 497364f2c4a8d766800e13819bcbab489ed03925..4903c303045e4a5a88421cdd01bb3f949bdfa8c0 100644
--- a/third_party/WebKit/public/web/WebFrameClient.h
+++ b/third_party/WebKit/public/web/WebFrameClient.h
@@ -51,6 +51,7 @@
 #include "public/platform/WebFileSystem.h"
 #include "public/platform/WebFileSystemType.h"
 #include "public/platform/WebLoadingBehaviorFlag.h"
+#include "public/platform/WebPageVisibilityState.h"
 #include "public/platform/WebSecurityOrigin.h"
 #include "public/platform/WebSetSinkIdCallbacks.h"
 #include "public/platform/WebStorageQuotaCallbacks.h"
@@ -710,6 +711,14 @@ public:
     // Mojo ----------------------------------------------------------------
     virtual ServiceRegistry* serviceRegistry() { return nullptr; }
 
+    // Visibility -----------------------------------------------------------

[kenrb, 2016/05/25 20:29:14]

Nit: there is one more hyphen in this line than the others. :)

[lfg, 2016/05/31 19:54:01]

Done.

+
+    // Returns the current visibility of the WebView.
+    virtual WebPageVisibilityState visibilityState() const
+    {
+        return WebPageVisibilityStateVisible;
+    }
+
 protected:
     virtual ~WebFrameClient() { }
 };